There are many regulations governing the safe operation of a hazardous process plant. A key part of the regulatory strategy is to ensure that operating companies take reasonable steps to formally analyze the risks to safety and take measures to reduce the risks to a very low level. For example, certain regulations require risks to human health to be quantified in terms of Fatal Accident Rate (FAR) which is measured in terms of the number of fatalities occurring during 1000 working lifetimes, approximated to 108 operating hours.
Standards and guidelines exist to support risk analysis and quantification. The International Electrotechnical Commission (IEC) 61508 is an international standard of rules intended to be a basic functional safety standard applicable to various industries. The IEC 61508 is titled Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems (E/E/PE, or E/E/PES). Additionally, the IEC 61511 is a specialization of IEC 61508, applicable to the process industry sector (not including the nuclear industry). IEC 61511 focuses attention on one type of instrumented safety system used within the process sector, namely the Safety Instrumented System (SIS) which is pervasive, but the standard does not provide requirements for other protective systems. The IEC 61511 standard provides a method of risk quantification, called the Layer of Protection Analysis (LOPA) method, that is used in the industry. Other examples of risk quantification methods include a Process Hazard Analysis (PHA) method or Quantitative Risk Assessment (QRA) method.